There is only one file type that uses the .NJB extension:
Nikon Photo Index File
Contains an index of photos taken with a Nikon digital camera; saved on the camera's SD memory card in the MISC folder; typically named "order.njb" by default.
NJB files are used to organize photos on the memory card and should not be opened by the user. They do not contain actual image data.
Updated: June 29, 2008